Assessment of sera for chromatin-immunoprecipitation

Chromatin-immunoprecipitation (ChIP) is a powerful technique for mapping the protein-DNA interactions that occur in living cells. The critical technical determinant for successful ChIP is the availability of an appropriate, "ChIP-grade" serum. Here we present a tech nique designed to assess whether sera are suitable for ChIP, and to quantify their efficiency relative to a positive internal reference. This approach is useful as a first step toward ChIP- on-chip or ChIP-sequencing, especially in the case of recently identified proteins for which no binding sites are yet known.